With particular but non-exclusive reference to offset printing presses, these basically comprise three cylinders: the plate cylinder, the blanket cylinder covered with rubber-coated fabric, and the impression cylinder. Below the said covering, the blanket cylinder comprises traditional under-packing formed: from individually removable (incompressible) gauged paper sheets for adapting the working diameter of the cylinder, and a separate under-blanket generally consisting of elastically compressible polybutadiene.
For levelling purposes, it is already known in the printing press sector to also use, as under-packing, polyester films coated with adhesive on one side.
The drawback of using paper and polyester is that both are rigid (hence not properly self-levelling), the former also not being fire-retardant.
From another patent of the same applicant (European patent 1,323,527), it is already known to use as under-packing a series of sheets (of paper or polyurethane) joined together by known pressure sensitive adhesive which enables the individual sheets to be removed to adapt the under-packing (of rubber-coated fabric) to the required thickness.